Core B provides a key resource for PPG investigators and has been heavily used in the past 10 years. It is anticipated that use will increase as PPGsupported research becomes more sharply focused on gene expression and gene regulation in the developing lung. The Core will provide: 1) scientific expertise and consultation as to selection of appropriate techniques and reagents, design of controls, and interpretation of findings; 2) training for PPG personnel in techniques needed for their work including immunostaining, in situ hybridization, microscopy, and image analysis; 3) key equipment and funds for equipment maintenance; 4) supplies commonly used in these procedures (slides, paraffin, etc.); and 5) a skilled technician to supervise equipment and teach personnel, standardize new methods, and update technical approaches. Immunohistochemical and in situ hybridization studies comprise much of the work done in the Core Lab, although Core personnel have experience with many other technics if needed. Written technical protocols have been prepared for these technics and are online for PPG investigators. All key equipment is available and functional. The Core has a Leitz microscope of exceptionally high quality that is equipped for brightfield, phase, darkfield, and fluorescence microscopy. The microscope is equipped with a video camera with input to a Macintosh G3 computer programmed by OpenLab software for image analysis including advanced measurements, specified counting, and fluorescence amplification.